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Issue 10, 2018
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A high voltage cathode of Na2+2xFe2−x(SO4)3 intensively protected by nitrogen-doped graphene with improved electrochemical performance of sodium storage

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Abstract

As a high-voltage and earth-abundant element, in recent years, alluaudite, Na2+2xFe2−x(SO4)3, has been regarded as a highly promising cathode material of sodium ion batteries with higher energy density. However, the critical environmental sensitivity and limited conductivity of this kind of sulfate-based (SO42−) polyanionic material has led to its poor crystal stability and inferior intercalation ability. Herein, we report the design of nitrogen-doped graphene under low temperature conditions as an evolutionary modification approach to prepare the Na2+2xFe2−x(SO4)3; namely, an alluaudite sulfate Na2+2xFe2−x(SO4)3@N-rGO composite was prepared by a facile co-precipitation method assisted by the nitrogen-doped graphene. It is therefore surprising that the three-dimensional graphene-based network provides continuous electron pathways; thus, the Na2+2xFe2−x(SO4)3@N-rGO composite exhibits improved electronic conductivity and excellent sodium insertion capability, as well as the electrochemical performance. As a result, it delivers a reversible capacity of 93.2 mA h g−1 with average redox potential of 3.8 V (vs. Na+/Na) at 0.05C; when the discharge rate increased to 10C, it delivers 56.3 mA h g−1 and an amazing capacity retention of 83% is achieved after 400 cycles. On the other hand, the doped nitrogen species plays a huge role on improving the electron-donating ability of the graphene layer, which effectively protects the easily oxidized host material from deterioration, giving the material longer stability in a normal oxygen-containing atmosphere. We believe that this work may lead to a promising, low cost, suitable sodium ion battery material for next-generation large-scale energy storage devices.

Graphical abstract: A high voltage cathode of Na2+2xFe2−x(SO4)3 intensively protected by nitrogen-doped graphene with improved electrochemical performance of sodium storage

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Publication details

The article was received on 20 Dec 2017, accepted on 12 Feb 2018 and first published on 12 Feb 2018


Article type: Paper
DOI: 10.1039/C7TA11110J
Citation: J. Mater. Chem. A, 2018,6, 4354-4364
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    A high voltage cathode of Na2+2xFe2−x(SO4)3 intensively protected by nitrogen-doped graphene with improved electrochemical performance of sodium storage

    W. Wang, X. Liu, Q. Xu, H. Liu, Y. Wang, Y. Xia, Y. Cao and X. Ai, J. Mater. Chem. A, 2018, 6, 4354
    DOI: 10.1039/C7TA11110J

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